Grab your iPhone (or any other high quality video recording device), and a buddy, and get him/her to film you paddling.
They will need to film you paddling from left to right, right to left, paddling towards the camera, and paddling away from the camera.
Try to have your buddy film you from as close as possible, and try to get at least 5 good strokes on each side during each sequence.
If you can use a tripod to steady the filming, it’s even better!
Video duration usually ends up between 5 and 10 minutes.
If you shoot from too far away, it is very hard for us to be able to properly evaluate your technique, and we may have to ask you to shoot it again.